Diary pro for Blackberry is one. Also if you do a google search you will find a bunch of free stuff. Also look at your apps on your phone you may find something in there? the search I did was (blackberry diary)

I found this one also Secret Diary (Blackberry) 3.0 This one is password protected. On your phone go to Blackberry apps -Productivity & Utilities- On-the -Go Productivity and it's in there for 16.99. This one seems to be a good one from what I have read, and it has 4 starts. I hope this helps you out?